A special mounting similar to “D” flange except with a machined
fit tenon recessed instead of protruding. Usually found on pumps.
When two or more DC motors are required to operate in parallel
– that is, to drive a common load while sharing the load equally among all motors
– they should have speed-torque characteristics which are identical.
The greater the speed droop with load, the easier it becomes to parallel
motors successfully. It follows that series motors will operate
in parallel easier than any other type. Compound
motors, which also have drooping speed characteristics (high regulation), will
generally parallel without special circuits or equalization.
It may be difficult to operate shunt or stabilized-shunt motors in parallel
because of their nearly constant speed characteristics.
Modifications to the motor control must sometimes be made before these
motors will parallel within satisfactory limits.
Is arranged for starting by first energizing part of the primary
winding and subsequently energizing the remainder of this winding in one or
more steps. The purpose is to reduce
the initial value of the starting current drawn or the starting torques developed
by the motor. A standard part winding
start induction motor is arranged so that one-half of its primary winding can
be energized initially and subsequently the remaining half can be energized,
both halves then carry the same current.
PERMANENT MAGNET SYNCHRONOUS (PMR) (HYSTERESIS SYNCHRONOUS)
A motor with magnets embedded into the rotor assemble, which
enable the rotor to align itself with the rotating magnetic field of the stator.
These motors have zero slip (constant speed with load) and provide higher
torque, efficiency and draw less current than comparable reluctance synchronous
motors.
Indicates the space relationships of windings and changing
values of the recurring cycles of AC voltages and currents. Due to the positioning (or the phase relationship)
of the windings, the various voltages and currents will not be similar in all
aspects at any given instant. Each winding
will lead or lag another in position. Each voltage will lead or lag another voltage
in time. Each current will lead or lag
another current in time. The most common
power supplies are either single- or three-phase (with 120 electrical degrees
between the tree-phases).
Reconnecting a motor’s winding in reverse to apply a reverse
braking torque to its normal direction of rotation while running. Although it is an effective dynamic braking
means in many application, plugging produces more heat than other methods and
should be used with caution.
A ration of one-minute meggar test to ten-minute meggar test.
Used to detect contaminants in winding insulation done typically on high
voltage V.P.I. motors, which are tested by water immersion.
In an AC motor, refers to the number of magnetic poles in the stator winding. The number of poles determines the motor’s speed.
In a DC motor, refers to the number of magnetic poles in the
motor. They create the magnetic field
in which the armature operates (speed is not determined by the number of poles).
Two- or Three-phase induction motors have their windings, one
for each phase, evenly divided by the same number of electrical degrees.
Reversal of the two-phase motor is accomplished by reversing the current
through either winding. Reversal of a Three-phase motor is accomplished
by interchanging any two of its connections to the line. Polyphase motors are used where a polyphase
(three-phase) power supply is available and is limited primarily to industrial
applications. Starting and reversing
torque characteristics of polyphase motors are exceptionally good. This is due to the fact that the different
windings are identical and, unlike the capacitor motor, the currents are balanced.
They have an ideal phase relation, which results in a true rotating field
over the full range of operation from locked rotor to full speed.
Identifies the type of power supply providing power to a DC
motor. Frequency, voltage, and type
of rectifier configuration.
A measurement of the time phase difference between the voltage
and current in an AC circuit. It is
represented by the cosine of the angle of this phase difference.
For an angle of 0 degrees, the power factor is 100% and the volt/amperes
of the circuit are equal to the watts (this is the ideal and an unrealistic
situation). Power factor is the ration of Real Power-KW
to total KVA or the ration of actual power (watts) to apparent power (volt amperes).
The winding of a motor, transformer or other electrical device
which is connected to the power source.
The principal function of a relay is to protect service from
interruption, or to prevent or limit damage to apparatus.
The maximum constant torque, which a synchronous motor will
accelerate into synchronism at, rated voltage and frequency.
The minimum torque developed by an AC motor during the period
of acceleration from zero to the speed at which breakdown occurs. For motors, which do not have a definite breakdown
torque, the pull-up torque is the minimum torque developed during the process
of achieving rated speed.